1. Field of the Invention
This invention relates to a method of preserving waste proteinaceous animal food materials and keeping them stabilized against decomposition and decay for extended periods of time when stored at room temperature and their use as a slow-release nitrogen fertilizer.
2. Description of the Prior Art
Fish waste; i.e., cannery wastes, have traditionally been disposed of by direct discharge into the nearest water body. New laws and regulations now prohibit this; however, canneries are currently allowed to collect their fish wastes, chop them and dispose of them by dumping into the ocean at required distances from shore. This is a costly disposal method and not entirely satisfactory. For one thing, the fish wastes cannot be stored for any length of time because of their rapid decay, which causes terrific odor problems, requiring land burial for disposal, which is even more costly than disposal in the ocean. There remains a need for a convenient way to utilize fish wastes for a useful purpose which, at the same time, will solve the waste disposal problem associated therewith.
Glycols are known to inhibit decay in proteinaceous materials such as fish wastes. U.S. Pat. No. 2,693,417 describes the use of glycol to preserve fish bait and herring. U.S. Pat. No. 3,904,774 discloses treating food and fish fillets with edible glycols to dehydrate and preserve the food and/or fish fillets. Before cooking, the glycol is washed from the treated food.
Fish fertilizer is generally manufactured as a liquid concentrate or as fish meal. Both forms have two disadvantages: odor and very rapid release of the nitrogen content of the composition when introduced into the soil. The rapid release of nitrogen results in short-lived effect of the fertilizer and, therefore, frequent applications are necessary. Care must also be used to prevent "burning" of the plants being fertilized by over-application. Odor is developed rapidly when these products are moistened for use. Synthetic slow-release nitrogen fertilizers, such as urea, are available; however, they are not natural products which contain many of the trace elements found in fish fertilizers.